K. T. Law

Light or sound can be confined in a tiny region of a crystal, like a pearl in a shell. Usually, two methods are used. The first is like a heavy ball in a pit: a particle with large mass simply cannot roll out. The second is a perfect cage of mirrors, where waves cancel each other everywhere except in the trap itself.

A water pipe: the wider it is, the more water flows through. In superconducting contacts — Josephson junctions (bridges through which current flows without resistance)—it's usually the same: the better the material conducts in its normal state, the larger the superconducting current that flows through it.